util/slicesx: add Partition function

Signed-off-by: Andrew Dunham <andrew@du.nham.ca>
Change-Id: If97995ca9ee9fad40f327420dcb1857dd7ea2315
pull/8313/head
Andrew Dunham 1 year ago
parent 2a9d46c38f
commit 62130e6b68

@ -42,3 +42,18 @@ func Shuffle[S ~[]T, T any](s S) {
s[i], s[j] = s[j], s[i] s[i], s[j] = s[j], s[i]
} }
} }
// Partition returns two slices, the first containing the elements of the input
// slice for which the callback evaluates to true, the second containing the rest.
//
// This function does not mutate s.
func Partition[S ~[]T, T any](s S, cb func(T) bool) (trues, falses S) {
for _, elem := range s {
if cb(elem) {
trues = append(trues, elem)
} else {
falses = append(falses, elem)
}
}
return
}

@ -44,6 +44,7 @@ func BenchmarkInterleave(b *testing.B) {
) )
} }
} }
func TestShuffle(t *testing.T) { func TestShuffle(t *testing.T) {
var sl []int var sl []int
for i := 0; i < 100; i++ { for i := 0; i < 100; i++ {
@ -64,3 +65,23 @@ func TestShuffle(t *testing.T) {
t.Errorf("expected shuffle after 10 tries") t.Errorf("expected shuffle after 10 tries")
} }
} }
func TestPartition(t *testing.T) {
var sl []int
for i := 1; i <= 10; i++ {
sl = append(sl, i)
}
evens, odds := Partition(sl, func(elem int) bool {
return elem%2 == 0
})
wantEvens := []int{2, 4, 6, 8, 10}
wantOdds := []int{1, 3, 5, 7, 9}
if !reflect.DeepEqual(evens, wantEvens) {
t.Errorf("evens: got %v, want %v", evens, wantEvens)
}
if !reflect.DeepEqual(odds, wantOdds) {
t.Errorf("odds: got %v, want %v", odds, wantOdds)
}
}

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